Basic substance for the manufacture of a permanent magnet

ABSTRACT

A PERNANENT MAGNET MATERIAL IS DISCLOSED HAVING A LARGE INTRINSIC COERCIVE FORCE (IHC) AND THUS STRONGLY RESISTANT TO DEMAGNETIZATION AND A LARGE ENERGY PRODUCT -(BH)MAX. THIS MATERIAL CONSISTS OF FINE PARTICLES HAVING PERMANENT MAGNET PROPERTIES AND CONSISTING ESSENTIALLY OF A COMPOUND M5R HAVING A HEXAGONAL CRYSTAL STRUCTURE. M IN THIS COMPOUND IS COBALT OR A COMBINATION OF COBALT WITH ONE OR MORE OF THE ELEMENTS FE, NI, AND CU WHILE R IS A RARE EARTH METAL (WHICH TERM INCLUDES Y) AND/OR TH. THESE PARTICLES ARE SURROUNDED WITH A METALLIC LAYER.   D R A W I N G

July 6 1971 K. H.J. BuscHow ErAL 3,591,428

BASIC SUBSTNCE FOR THE MANUFACTURE OF A PERMANENT MAGNET Filed Nov. 26, 1968 L Acfw United States Patent O 3,591,428 BASIC SUBSTANCE FOR THE MANUFACTURE F A PERMANENT MAGNET Kurt Heinz Jurgen Buschow, Pieter Aart Naastepad, Wilhelmus Antonius Johannes Josephus Velge, and Johannes Hendrikus Nicolaas van Vucht, Emmasingel, Eindhoven, Netherlands, assignors to U.S. Philips Corporation, New York, N.Y.

Filed Nov. 26, 1968, Ser. No. 778,981 Claims priority, application Netherlands, Dec. 21, 1967, 6717442 Int. Cl. H01f 1/08 U.S. Cl. 14S-31.57 12 Claims ABSTRACT OF THE DISCLOSURE A permanent magnet material is disclosed having a large intrinsic coercive force (IHC) and thus strongly resistant to demagnetization and a large energy product (BH),CX. This material consists of line particles having permanent magnet properties and consisting essentially of a compound MR having a hexagonal crystal structure. M in this compound is cobalt or a combination of cobalt with one or more of the elements Fe, Ni, and Cu while R is a rare earth metal (which term includes Y) and/ or Th. These particles are surrounded with a metallic layer.

The invention relates to a basic substance for the manufacture of a permanent magnet consisting of ne particles in themselves having permanent magnetic properties, the essential constituent being a compound of hexagonal structure the existence region of which is integral with the existence region of the compound MIR in the system MR, wherein M designates Co or a combination of Co with one or more of the elements Fe, Ni and (h1 and R designates one or more of the rare earth metals and/or Th. The rare earth metals are considered in this respect to include also the element Y.

Such basic materials are `known from Dutch patent application No. 6608335 which has been opened for public inspection. They exhibit a high magnetic anisotropy in conjunction in most cases with a high magnetization.

Since a basic substance for the manufacture of permanent magnets consisting of fine particles of this basic substance must satisfy the requirement that the intrinsic coercive force IHC and the magnetization fr should be sufficiently high, the aforesaid MI-,R compounds can be successfully employed to this end.

Such a known basic substance may be formed by line particles of the compound SmCo5. Depending upon the degree of deformation and size these particles may have an IHC of 10,000 oersted (oe.) and a 24K CC of 90 ergs/ g. oe. and an IHC of 10,000 oe.

A basic substance according to the invention is characterized in that the particles are surrounded by a metallic layer.

The term metallic is dened herein as consisting of a metal, an alloy of metals or an alloy of one or more metals with one or more metalloids.

Such basic substances according to the invention, due to their being plated, exhibit an increase in the IHC.

The following values measured on SmCo5 are illustrative of this improvement in IHC of a basic substance according to the invention. The measurements are based on a non- 3,591,428 Patented July 6, 1971 ice plated SmCo5 powder having an IHC of 6500 oe. After plating the following results were obtained:

The invention will be described with reference to the drawing in which the sole gure shows graphs relating the magnetic properties to the thickness of the metal layer.

It should be noted that the magnetization of the plated particles depends upon the thickness of the surrounding layer. As is indicated in the graph I of the 025K CC., as compared with that of non-plated basic material, rst increases with an increasing thickness of the layer-which involves a longer plating time t-and then decreases. Graph II indicates the relationship between the IHC and the plating time t.

The invention furthermore relates to a method of manufacturing a basic substance of the kind set forth in as much as the layers consist of one or more metals of the EMF series nobler than Zn, alloyed or not alloyed with metal-loids.

In this method the cast made by melting the constituents and by subsequent cooling is relined. The refinement is continued until the particles have the desired magnetic properties, for example, the desirable IHC and orientability.

The method according to the invention is characterized in that the particles are first etched, then washed, if necessary, and inally introduced into a bath containing a solution of salts appropriate for depositing chemically, or electro-chemically, the desired layer on the surface of the particles.

The following examples are illustrative.

EXAMPLE I 35 gms./ liter of NiSO.I.7H2O, 30 gms/liter of amino-acetic acid, l5 gms/liter of NaH2PO2-H2O.

The pH value was 4.5 (to be adjusted with NHIOH) and the temperature was 50 C.

EXAMPLE II The application of a Co-P layer to SmCoI` particles. First etching was carried out as described in Example I. The solution contained:

27.1 gms/liter of C0Cl26H2O, 45.3 gms/liter of NHICI,

90 gms/liter of Na-citrate-ZHIO, 9 gms/liter of NaHZPOg-HZO.

By means of NI-I4OH the pH value was brought to 8.5.

At C. the rate of growth of the layer thickness was 0.005 ,tt/min.

3 EXAMPLE In The application of an Ni-Co-P-layer. First etching was carried out as in Example I.

The composition of the solution was like that of Example I with the addition of 12 gms/liter of COSOI.

Plating was carried out at a pH value of about 7 and at a temperature of 60 C.

EXAMPLE IV The application of a Cu-layer. First etching was carried ou't as described in Example I.

The solution contained:

200l gms/liter of CuSO4, 60 gms./ liter of H2804.

Plating was carried out at a temperature of 20 C.

The invention furthermore relates to a permanent magnet made from the aforesaid basic substance. Such a magnet has a higher IH,3 than a magnet made from tine, nonplated particles of the same compound and will therefore exhibit an improved resistance to demagnetizing Iields.

EXAMPLE V SmCo5-particles are surrounded by a metallic Cu-layer by means of sputtering For one hour, Cu was sputtered on to the SmCo5, resulting in a Cu-layer having a thickness of 0.24%

The values of -a' and IHC, were raised from 91.5 to 93 erg/gr. e. respectively from 6500 oe. to 9600 oe.

EXAMPLE VI SmCo-particles were surrounded by an Ag-layer by means of a sputtering process of 1 hour, resulting in a layer of a thickness of 0.36/1.

The oand IHc-values were raised from 91.5 erg/ gr. oe. to 94.5 erg/ gr. oe. respectively from 6500 oe. to 10,100 oe.

A permanent magnet made from the basic substance according to the invention may also be anisotropic. Also this anisotropic magnet will exhibit a higher resistance to a demagnetizing eld, while in addition the product (BH)max may be higher.

An example of an anisotropic permanent magnet according to the invention is a magnet consisting of SmCo5 particles plated with an Ni-P-layer. This magnet has a (BH)max of 9X l06 G 0e. and IHc of 17,000 oe., whereas a magnet made from non-plated, but otherwise identical SmCo5 particles has a (BPDIm,x of 7 106 G oe. and an IHc of 6500 oe.

Particularly when an anisotropic permanent magnet is made from a basic substance according to the invention, the advantage of these substances is conspicuous. It is known that a basic substance for the manufacture of an anisotropic permanent magnet has to satisfy not only requirements with respect to a sufficiently high IHc and, which Values are raised both by suitable plating, but also the requirement that in a magnetic field the particles should allow for satisfactory orientation. A measurement for the orientability of the particles is the ratio Ir/Is, wherein Ir is the remanence and Is is the saturation magnetization per unit of volume. It has been found that during the rening process for obtaining the fine particles after a given time the 1/1s drops. In order to attain optimum I'Hc Values it is, however, necessary to continue the rcning process for a given period of time. Unfortunately, the drop of the ratio Ir/Is starts already before the optimum IHC.

Since, however, the basic substance plated in accordance with the invention has a considerably higher I'I-Ic than a comparable non-plated basic substance, a shorter period of the refining process may be chosen so that the Ir/Is has not yet, or has scarcely diminished. The resultant nonoptimum IHc is then raised by the plating process to an extent such that the nal IHc of the plated powder largely exceeds that of the non-plated particles. The advantage of the improved orientability of the particles becomes manifest in the higher (BH)max product of the magnet.

While the invention has been described with reference to particular examples and applications thereof, other embodiments will be apparent to those skilled in this art without departing from the spirit and scope of the invention which is defined in the appended claims.

What is claimed is:

1. A basic substance for the manufacture of a permanent magnet consisting of fine particles themselves having permanent magnetic properties, the essential constituent `being a compound of hexagonal structure, the existence region of which is integral with the existence region of the compound M5R of the system MR, wherein M is an element selected from the group consisting of Co, a combination of Co with at least one of the elements Fe, Ni and Cu, and wherein R is selected from the group consisting of at least one of the rare earth metals, Th, and the combination of Th with at least one of the rare earth metals, each said particles being coated with a layer of a metal which increases the coercive force of said particles.

2. A basic substance as claimed in claim 1 in which the M is Co, R is Sm and the metallic layer contains Ni.

3. A basic substance as claimed in claim 2 in which the nickel is alloyed with an element selected from the group consisting of P and B.

4. A basic substance as claimed in claim 2 in which the metallic layer consists of nickel.

5. A basic substance as claimed in claim 1 in which M is Co, R is Sm and the metallic layer contains Co.

6. A basic substance as claimed in claim 5 in which the cobalt is alloyed with an element selected from the group consisting of P and B.

7. A basic substance as claimed in claim 5 in which the metallic layer consists of Co.

8. A basic substance as claimed in claim 1 in which M is Co, R is Sm and the metallic layer contains Sn.

9. A basic substance as claimed in claim 8 in which the Sn is alloyed with an element selected from the group consisting of Zn and Cd.

10. A basic substance as claimed in claim 8 in which the metallic layer consists of Sn.

11. A basic substance as claimed in claim 1 in which M is Co, R is Sm and the metallic layer consists of Cu.

12. An anisotropically magnetized permanent magnet consisting of magnetically oriented particles consisting essentially of a basic substance as claimed in claim 1, said magnet having a higher (BH)maX value than a like magnet consisting of particles of the same composition without a metallic layer thereover.

References Cited UNITED STATES PATENTS 2,967,794 1/1961 Coxe 148-3 1.57K

3,424,578 l/l969 Strnat et al. -213 3,463,678 8/1969 Becker 148-105 FOREIGN PATENTS 736,923 6/1966 Canada 204-23 6608335 12/1967 Netherlands 14S- 31.57

HYLAND BIZOT, Primary Examiner G. K. WHITE, Assistant Examiner U.S. Cl. X.R. 148-103; 204--23 

